I recently feel in love with spinel instead of sapphire. However, all spinels I have seen so far have a serious tilt window worse than the average sapphire. From what I have read online, it was due to the refractive index of spinel is lower than sapphire's refractive index.
I wonder if certain precision cut spinel may have smaller tilt window. Thank you
Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
Yes if you have the same exact cut, proportions on each of your two samples, the tilt performance is most likely going to be different. You can run the designs through software to compare this performance.
The RI of sapphire and spinel is so close I doubt you would notice much difference. I think what you are seeing is not due to the refractive index but the cutting angles used in the particular stones you looked at.
The RI of sapphire and spinel is so close I doubt you would notice much difference. I think what you are seeing is not due to the refractive index but the cutting angles used in the particular stones you looked at.
What do you mean it is due to the cutting angles? Actually, Gene I saw one of your beautiful work posted on a gemstone forum, and it has the same tilt window problem as most spinel I have seen. I owned two sapphires precision cut by you, and they did not have this huge tilt window problem.
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Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
Maybe a 30 degree tilt instead of a 10 degree will reflect the image better. Also software uses absolute numbers to calculate the results, the actual stone is cut on machine by a person, so as precise as you say it is cut, it is only as precise as the machine and the cutter. Not the software. JMHO.....
Maybe a 30 degree tilt instead of a 10 degree will reflect the image better. Also software uses absolute numbers to calculate the results, the actual stone is cut on machine by a person, so as precise as you say it is cut, it is only as precise as the machine and the cutter. Not the software. JMHO.....
Wasn't it your idea to run the design through software to see the difference?
Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
Precision Gem wrote:
glhays wrote:
Maybe a 30 degree tilt instead of a 10 degree will reflect the image better. Also software uses absolute numbers to calculate the results, the actual stone is cut on machine by a person, so as precise as you say it is cut, it is only as precise as the machine and the cutter. Not the software. JMHO.....
Wasn't it your idea to run the design through software to see the difference?
Yes. And I also said " the tilt performance is most likely going to be different" which it is slightly and the falloff is more drastic in Spinel.
My comment about a 30 degree tilt is based solely on the image the poster posted, which looks to me like the two stones in the image are angled more than 30 degrees. A majority of gemstones tilted past 10 degrees are prone to a dramatic visible window and performance drop.
What is the drop off between the two when the tilt is higher is the thought I had and again based only on the posters post of why the big difference. Yes I can run the performance tests myself between the two species and have but we both know that the design and angles will dictate the results, and it appears you have the actual design to test.
Here you go in Quartz. Not a design I would cut in quartz.
For me, any designs I cut in Sapphire, I would also cut with no changes in Spinel. From the plots there is essentially no difference. If I didn't identify them, you would never know which is which.
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